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Page last updated at 16:08 GMT, Wednesday, 2 February 2011
Parrots prefer 'left handedness'
By Emma Brennand
Earth News reporter

Sulphur-crested cockatoo holding food in left hand.
Young parrots tend to experiment with both feet before they settle on one.

Handedness was once a trait believed to be unique to humans.

But it turns out that parrots prefer to use one side of their body more than the other too.

A study published in the journal Biology Letters has found that almost all parrots prefer to use either their left eye and left foot, or their right eye and foot.

Each bird becomes "left or right footed" in this way to help them scrutinise food, researchers believe.

The discovery adds to growing evidence that even lower vertebrates prefer to use one side of the body more often to perform routine tasks.

Young Sulphur-crested cockatoos all end up being left-footed, but when they first come out of the nest they are equally clumsy with both
Dr Culum Brown
Macquarie University, Australia

A team of researchers from Macquarie University, Sydney, Australia studied the eye and foot preferences of 322 birds across 16 species of Australian parrot.

"We looked at the eye preferences these birds have," explains Dr Culum Brown, the project's lead researcher.

"For every species except one, there was a very strong correlation between the eye they view food with and the foot they use to pick it up."

The exception is the cockatiel, the smallest species of Australian cockatoo, which showed no relationship between eye and foot preference.

The researchers suggest this difference may have evolved because of differences in cockatiel foraging behaviour, as cockatiels graze on small grass seeds that may require little coordination between the eyes and feet.

Lefty or righty?

Dr Brown's research shows that in four species of the 16, almost every individual member of each parrot species was either left handed or "left footed", or right footed, showing the preference for using one side has somehow become fixed in the population.

"Indeed we have yet to find a right handed Sulphur-crested cockatoo, says Dr Brown.

"It is interesting because there are very few examples of extreme foot preferences in any animals except humans."

Foot preference also differed within parrot species families, with some species in the same family being left footed and others right footed.

In humans, approximately 10 per cent of the population is left handed.

Previous research has shown that handedness in humans reflects the use of one brain hemisphere over the other, a behaviour scientists call "laterality".

Preference for one limb suggests that an animal's brain function is also lateralised, with one side of the brain dominating control of certain tasks.

The team believes the hemisphere of the brain involved in the food selection of parrots may also be the area responsible for "footedness".

"We think this is probably true of lots of animals, perhaps even humans. " Dr Culum told BBC News.

"It is a reflection of the dominant hemisphere that is involved in analysing information about the potential food item."

He adds: "Just like in human children, young parrots tend to experiment with both hands before they settle on one hand or the other."

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